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Infraorder Simiiformes


The infraorder Simiiformes was named in...

Distinguishing Characteristics

Plesiomorphies

Dichromatic (two-color) vision, inherited from basal primata, preserved in platyrhini. Modified to trichromatic (three-color) vision in catarhini.

Apomorphies

The diagnostic features used to distinguish monkeys (simiiformes) from other simians (haplorhines), include:


Absent sensory whiskers
Single pectoral pair of mammae
Unsheathed, pendulous penis
Bony plate in back of orbit
Longer gestation
Absent rhinarium
Fully binocular vision
Increased encephalization (see neoteny, below)
More rounded cranium (see neoteny, below)

Neoteny

In addition, simiiformes are neotenous compared to other primates. This means that we retain a more juvenile appearance.

Neoteny
Figure 1 — Pug (top left), chihuahua (mid left), grey wolf (bottom left), marmoset (top right), tarsier (mid right), and ring-tailed lemur (bottom right). Just as chihuahuas and pugs are neotenous wolves, so too are haplorrhines neotenous primates. And between the two groups of haplorrhines, the simiiformes appear to be even more neotenous than the tarsiiformes.

Extant Simiiformes

Capuchin
Platyrrhines
Langurs
Catarrhines

References

Williams, B. Kay, R. Kirk, C. New perspectives on anthrpoid origins. PNAS March 16, 2010 107 (11) 4797-4804; https://doi.org/10.1073/pnas.0908320107


Immediate Phylogeny

Parent Group
Haplorhini

Sister Groups
Tarsiiformes (Tarsiers)

Daughter Groups
Catarrhini
Platyrrhini

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Taxonomy

DomainEucarya

KingdomMetazoa

PhylumChordata

ClassMammalia

OrderPrimata

SubrderHaplorhini

InfraorderSimiiformes

Parvorders
Catarrhini
Platyrrhini

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Recommended Links
Fossil Hominids:The Evidence for Human Evolution

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Evolution Links
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